Prior art of possible relevance includes U.S. Pat. Nos. 2,378,580 issued June 19, 1945 to Prause et al and 2,378,938 issued June 26, 1945 to McCoy.
As mentioned previously, the invention herein, while it may be utilized with efficacy in a variety of environments is, in its best mode, comtemplated to be employed in a system to provide emergency feathering of a ram air turbine. Such turbines are typically utilized to drive a load in response to rotary motion generated by the passage of a fluid, usually air, across turbine blades. In the usual case, means are provided for adjusting the pitch of the turbine blades to achieve a desired rotational output, typically constant speed, for varying loads and conditions.
In the usual case, a small motor, frequently a stepping motor, is utilized to make fine adjustment of the pitch of the blades in response to suitable control signals. For normal operation, such a system works well. However, in some instances, pitch adjustment through the use of such a small motor cannot be achieved with sufficient rapidity for the particular situation involved.
For example, if one considers the situation where the load on the turbine shaft is suddenly removed or drastically reduced, the turbine, now being unloaded, may be driven into a damaging overspeed condition before the pitch of the blades can be adjusted sufficiently to prevent such from happening by the small motor. This occurrence is not unlikely where the turbine blades are at a fine pitch when the load is removed and must be driven to a course pitch or feathered position to prevent overspeed from occurring.
The present invention is directed to overcoming the foregoing problem.